The prior art related to window apparatus includes a type of window which is conventionally known as a double-hung window. This type of window includes a frame or jamb assembly, which is attached to the wall of a building, and usually two window frames or sashes which are mounted on the jamb assembly and which slide in a vertical direction relative to the jamb assembly. The window frames support panes of glass or plastic glazing material. An important type of double-hung window includes provisions for tilting the individual window frames inwardly for the purpose of cleaning.
Although the tilting type of double-hung window has found extensive application in private homes and other relatively small buildings, the application of this type of window to large office and apartment buildings has not been practical because of the inability of such windows to withstand the wind loading normally encountered by such buildings.
Another disadvantage of the conventional tilting type of double-hung window is that this type of window provides only limited security against forced entry by a person who pushes against the window frames in a direction which causes them to tilt and by doing so overcomes the relatively weak anti-tilt locks usually provided on such windows.